IBM researchers have already installed the mounting hardware for a jumbo cryostat big enough to hold a quantum computer with 1 million qubits.
Connie Zhou/IBM
For 20 years scientists and engineers have been saying that “someday” they’ll build a full-fledged quantum computer able to perform useful calculations that would overwhelm any conventional supercomputer. But current machines contain just a few dozen quantum bits, or qubits, too few to do anything dazzling. Today, IBM made its aspirations more concrete by publicly announcing a “road map” for the development of its quantum computers, including the ambitious goal of building one containing 1000 qubits by 2023. IBM’s current largest quantum computer, revealed this month, contains 65 qubits.
“We’re very excited,” says Prineha Narang, co-founder and chief technology officer of Aliro Quantum, a startup that specializes in code that helps higher level software efficiently run on different quantum computers. “We didn’t know the specific milestones and numbers that they’ve announced,” she says. The plan includes building intermediate-size machines of 127 and 433 qubits in 2021 and 2022, respectively, and envisions following up with a million-qubit machine at some unspecified date. Dario Gil, IBM’s director of research, says he is confident his team can keep to the schedule. “A road map is more than a plan and a PowerPoint presentation,” he says. “It’s execution.”
IBM is not the only company with a road map to build a full-fledged quantum computer—a machine that would take advantage of the strange rules of quantum mechanics to breeze through certain computations that just overwhelm conventional computers. It has been playing catch-up to Google, which 1 year ago grabbed headlines when the company announced its researchers had used their 53-qubit quantum computer to solve a particular abstract problem that they claimed would overwhelm any conventional computer—reaching a milestone known as quantum supremacy. Google has its own plan to build a million-qubit quantum computer within 10 years, as Hartmut Neven, who leads Google’s quantum computing effort, explained in an April interview, although he declined to reveal a specific timeline for advances.
IBM’s declared timeline comes with an obvious risk that everyone will know if it misses its milestones. But the company decided to reveal its plans so that its clients and collaborators would know what to expect. Dozens of quantum-computing startup companies use IBM’s current machines to develop their own software products, and knowing IBM’s milestones should help developers better tailor their efforts to the hardware, Gil says.
One company joining those efforts is Q-CTRL, which develops software to optimize the control and performance of the individual qubits. The IBM announcement shows venture capitalists the company is serious about developing the challenging technology, says Michael Biercuk, founder and CEO of Q-CTRL. “It’s relevant to convincing investors that this large hardware manufacturer is pushing hard on this and investing significant resources,” he says.
A 1000-qubit machine is a particularly important milestone in the development of a full-fledged quantum computer, researchers say. Such a machine would still be 1000 times too small to fulfill quantum computing’s full potential—such as breaking current internet encryption schemes—but it would big enough to spot and correct the myriad errors that ordinarily plague the finicky quantum bits.
A bit in an ordinary computer is an electrical switch that can be set to either zero or one. In contrast, a qubit is a quantum device—in IBM’s and Google’s machines, each is a tiny circuit of superconducting metal chilled to nearly absolute zero—that can be set to zero, one, or, thanks to the strange rules of quantum mechanics, zero and one at the same time. But the slightest interaction with the environment tends to distort those delicate two-ways-at-once states, so researchers have developed error-correction protocols to spread information ordinarily encoded in a single physical qubit to many of them in a way that the state of that “logical qubit” can be maintained indefinitely.
With their planned 1121-qubit machine, IBM researchers would be able to maintain a handful of logical qubits and make them interact, says Jay Gambetta, a physicist who leads IBM’s quantum computing efforts. That’s exactly what will be required to start to make a full-fledged quantum computer with thousands of logical qubits. Such a machine would mark an “inflection point” in which researchers’ focus would switch from beating down the error rate in the individual qubits to optimizing the architecture and performance of the entire system, Gambetta says.
IBM is already preparing a jumbo liquid-helium refrigerator, or cryostat, to hold a quantum computer with 1 million qubits. The IBM road map doesn’t specify when such a machine could be built. But if company researchers really can build a 1000-qubit computer in the next 2 years, that ultimate goal will sound far less fantastical than it does now.